Plant for the production of paper logs

ABSTRACT

Plant for the production of paper logs, including a number of operating units configured to produce logs of paper material starting from a web of paper material unwound from one or more corresponding reels and slaved to a control unit that, in turn, is configured for driving the operating units such that each of them has a predetermined production speed. The said control unit is programmed to process data contained in a database individually associated with each reel and representative of defects classified according to a predictive classification based on the effects of the defects in the production of the logs and further representative of the location of defects on the web unwound from the reel. The control unit receives position data related to the instantaneous diameter of the reel from a corresponding detection means. The control unit is programmed to modify the production speed in function of the instantaneous position and of the class of each of the defects.

The present invention relates to a plant for the production of paper logs. During the production of the paper webs, between the Yankee drier and the rewinder of the paper machines, optical devices are normally provided for detecting the presence of defects, locating them and recording their shape on corresponding photographic images. A data file is also produced, associated with the specific reel, in which the defect positions are stored. The data of said file correspond to the positions and possibly also to the density of the defects intended as the number of defects per unit area. When the reel is used in a paper converting plant, for example to produce logs from which rolls of toilet paper or rolls of kitchen paper are made, the operators adjust the speed of the processing machines or even stop them, depending on the defect data associated with the reels in use and recorded in the respective files. In practice, knowing that at a given diameter of a reel in use there are defects capable of compromising the production of logs, the operators, when this diameter is reached, slow down the machines or stop the production.

However, this procedure is inefficient as it depends significantly on the experience and attention of the operators.

The main object of the present invention is to overcome the aforementioned drawbacks.

This result has been achieved, in accordance with the present invention, by adopting the idea of implementing a plant having the characteristics indicated in claim 1. Other features of the present invention are the subject of the dependent claims.

Thanks to the present invention it is possible to increase the degree of automation of the production of logs to a significant extent, freeing the efficiency of the process from the level of experience of the operators. In this way, it is possible to increase the quality of finished products by reducing waste because the paper used is subject to stresses regulated on the basis of the previously detected defects. Safety at work is also increased thanks to the substantial increase in production automation which reduces operators' intervention.

These and further advantages and characteristics of the present invention will be better understood by any person skilled in the art, thanks to the following description and to the attached drawings, provided as an example but not to be considered in a limiting sense, in which:

FIG. 1 shows a schematic simplified view from the above of a plant for the production of paper logs;

FIG. 2 schematically represents a series of possible defects of a web used in the plant of FIG. 1.

In accordance with the present invention, it is envisaged to associate a data file to each parent reel (1) which identifies the position and the class of any defects detected in a production step of the same parent reel (1). The class of defects is determined on the basis of a pre-established criterion that takes into account the possible negative effects of the defects during the use of the reel (1) in a paper converting plant. The data file is entered in a programmable unit (2) that processes it and controls the actuation of one or more operating units (A, B, C) of the plant based on the class and position of each defect. In practice, according to the class and the position of each defect, the control unit (2) actuates the operating units (A, B, C) so as to cause a slowing down or possibly a stop of the same units (A, B, C).

For example, with reference to FIG. 1, the operating units are an unwinder (A), an embosser (B) and a rewinder (C) arranged one after the other along a paper feed direction (FW). The unwinder (A) is a machine configured to support at least one reel (1) and allow it to unwound. The embosser (B) is a machine located downstream of the unwinder (A), in which the paper is embossed.

The rewinder (C) is a machine in which the paper web coming from the embosser (B) is rewound to produce rolls or logs with a smaller diameter than that of the parent reel (1). Otherwise, the operating units may be more simply an unwinder (A) and a rewinder (C) arranged one after the other along said direction (FW). In both cases, said units are known per se and do not require mechanical or structural modifications for the practical implementation of the invention. It is understood that the number of operating units constituting the paper converting plant is not a limiting factor of the invention here disclosed. As previously mentioned, the class of defects presented by the parent reel (1) is defined according to the possible negative effects of the use of the paper in a paper converting plant. For example, the classes of the defects can be four in number (I, II, III, IV) whose negative effects during the use of paper in a paper converting plant are progressively less important. For example, a possible classification of defects related to the position of the defects can be defined through the following table

DIAMETER PROGRAMMED (mm) DEFECT CLASS ACTION 2100-2140 I STOP 1100-1130 II SPEED REDUCTION (−50%) AND LOG DISCARDED 800-810 III SPEED REDUCTION (−30%) AND LOG DISCARDED 100-105 IV SPEED REDUCTION (−30%) WITHOUT DISCARDING THE LOG

In the example table above, the class I defect is such as to impose the stop of the plant. For example, the class I defect may correspond to a discontinuity (10) in the paper web (W) fed by the reel (1) of any shape and area greater than 70 cm² or to a discontinuity (11) that is oriented along a direction (T) substantially transverse to the paper web and having a length (h11) equal to at least 20% of the width (LW) of the web (W) or to a series of discontinuities (12) individually of reduced width but contained in an area (A12) such that the sum of the areas of the individual discontinuities in relation to the area (A12) is greater than or equal to 0.2 (ΣA_(i)/A12≥0.2, where Ai is the area of the single discontinuity and A12 is the reference area).

Similarly, for example, the class II defect may correspond to a discontinuity (13) in the paper web fed by the reel (1) of any shape and area comprised between 70 cm² and 50 cm² or to a discontinuity (14) oriented along a direction (T) substantially orthogonal to the web and having a length (h14) comprised between 20% and 10% of the width (LW) of the web (W) or to a series of discontinuities (15) individually of reduced extension but contained in a area (A15) such that the sum of the areas of the individual discontinuities in relation to the area (A12) is between 0.2 and 0.1 (0.2>ΣA_(i)/A15≥0.1, where Ai is the area of the single discontinuity and A15 is the reference area). Similarly, for example, the class III defect may correspond to a discontinuity (16) in the paper web fed by the reel (1) of any shape and area comprised between 50 cm² and 30 cm² or to a discontinuity (17) oriented along a direction (T) substantially transverse to the web and having a length (h17) comprised between 10% and 5% of the width (LW) of the web (W) or to a series of discontinuities (18) individually of reduced extension but contained in a area (A18) such that the sum of the areas of the individual discontinuities in relation to the area (A18) is between 0.1 and 0.05 (0.1>ΣA_(i)/A18≥0.05, where Ai is the area of the single discontinuity and A18 is the reference area).

Finally, for example, the class IV defect may correspond to a discontinuity (19) in the paper web fed by the reel (1) of any shape and area comprised between 30 cm² and 10 cm² or to a discontinuity (20) oriented along a direction (T) substantially orthogonal to the paper web and having a length comprised between 5% and 2% of the width (LW) of the paper web (W) or to a series of discontinuities (21) individually having a reduced extension such that the sum of the areas of the individual discontinuities in relation to the area (A21) is between 0.05 and 0.03 (0.05>ΣA_(i)/A21≥0.03, where Ai is the area of the single discontinuity and A21 is the reference area).

In practice, with reference to the defects (12, 15, 18, 21) the classification criterion is based on their superficial density. It is understood that the defects of the web (W) can be classified according to any other criterion. Similarly, the programmed actions may also be different depending on the quality of the desired finished product and the type of paper. In other words, the values and the corresponding programmed actions provided previously by way of example may vary according to the structural characteristics of the paper and/or according to the desired result in terms of quality of the finished product. In practice, a plant according to the present invention comprises several operating units (A, B, C) cooperating with each other to produce logs of paper material with a predetermined operating production speed using at least one paper web (W) fed by parent reel (1), wherein said units (A, B, C) are controlled by a control unit (2) programmed to stop the units themselves or reduce their operating speed according to the position and type of defects (10-21) presented by the web (W) and recorded in a database used by the control unit (2) to control the operating speed of said units (A, B, C) according to a predetermined control criterion which associates each defect (10-21) with a corresponding mode of operation of the units controlled by it.

The database of the defects presented by the web (W) is acquired in a production phase of the parent reel (1) and is used in a subsequent phase of use of the same.

The control unit (2) synchronously drives the units (A, B, C) that make up the production line of the logs on the basis of the position and class of the defects of web (W) acquired during the production of the latter.

In practice, by means of optical inspection systems normally used to control the quality of the product in the paper machines, the defects of web (W) are detected, located and recorded during the production of the web.

The classification of the defects thus detected and localized, in accordance with the present invention, is established according to a criterion which, as said above, attributes to the various types of defects a negative effect in the phase of production of the logs of progressively smaller entity. For example, with reference to the example table provided above, a class I defect can determine the tearing or breaking of the web during the production of the logs even in case of slowing down of the units (B, C) that use it. Or, for example, a class II or class III defect can cause a web tear or break if the production speed of the units (B, C) is not decreased by 50% or 30% but in any case the quality of the logs prevents their commercialization because of the defects presented. Or again, for example, a class IV defect can cause a web tear if the production speed of the units (B, C) is not decreased by 30% but the quality of the log produced is still sufficient to allow its commercialization. For example, the normal production speed, i.e. the production speed in the absence of classified defects, is 650 meters of web per minute.

The position of each defect of the web (W) is in direct correlation with the instantaneous diameter of the reel (1). The instantaneous diameter of the reel (1) can be detected, for example, by an encoder (3) connected on the axis of the same reel on the basis of the unwinding speed of the web or also by photocells (4) or equivalent optical devices arranged in front of a reel end.

The outputs of the encoder (3) or photocells (4) are connected to the input of the control unit (2). For simplicity, in FIG. 1 the connection between the photocells (4) and the control unit (2) is not shown.

The defect database is stored, for example, in a server (5) connected to the control unit (2). The server (5) has a memory in which the defect database of each reel placed in the unwinder (A) is stored. Alternatively, the same control unit (2) has a memory in which the defect database of each reel located in the unwinder (A) is stored.

Therefore, the control unit (2) continuously receives the data relative to the instantaneous diameter of the reel (1), i.e. relative to the “length” of the unwound web, and activates the actions programmed on the units (A, B, C) in function of the possible defect corresponding to the instantaneous diameter of the reel itself.

In FIG. 1 the “2P” block indicates a software program, residing in the control unit (2), which processes the input data relative to the instantaneous diameter of the reel (1) and the data contained in the defects database, and provides instructions to the control unit (2) to implement the actions previously indicated on the basis of a corresponding actions execution algorithm. The control unit (2) is connected to the drivers (AA, AB, AC) of the units (A, B, C) controlled by it. The “5D” block indicates the defect database stored in the server (5).

If the paper material wound in the rewinder (C) is made up of several plies fed by more than one parent reel, then the control unit (2) uses the defect database of each web and intervenes to activate the programmed action independently of the specific ply presenting the defects of the class corresponding to the programmed action. In other words, even if only one ply has defects of a given class, the control unit (2) commands the activation of the corresponding programmed action even if the other plies do not show any defects. In other words, the web (W) used for the production of logs can be formed of several plies, each of which is carried out by a corresponding reel and each reel is associated with a corresponding database of defects according to what has been described above. In this case, the control unit (2) activates the aforementioned programmed actions based on the individual databases. For example, the plies can be joined together in the embosser (B) according to methods known per se to those skilled in the art.

In more general terms, therefore, a plant for the production of logs of paper material comprises several operating units (A, B, C) configured to produce logs of paper material starting from a paper web (W) fed by one or more corresponding reels (1) and controlled by a control unit (2) which, in turn, is configured to drive said operating units so that each of them has a predetermined production speed; said control unit (2) is programmed to process data contained in a database (5D) individually associated with each reel (1) and representative of defects (10-21) classified according to a predictive classification (I, II, III, IV) based on the effects of the defects themselves in the production of the logs and representative of the position of the defects on the web that unwounds from said reel; the control unit (2) receives position data correlated to the instantaneous diameter of the reel by means of corresponding detection means (3; 4), and the control unit (2) is programmed to modify said production speed as a function of the instantaneous position and class (I, II, III, IV) of each of the said defects (10-21).

In accordance with the present invention it is therefore possible to use the data related to the defects of the web (W) unwound from the reel (1) to drive synchronously the operating units of the system (A, B, C) according to automatic procedures for managing the programmed actions, reducing the possible negative effects of the defects in the production of paper logs.

It is also possible to program the control unit (2) in such a way that the predetermined production speed is modified according to a predetermined deceleration ramp until a second speed, lower than the production speed, is reached (that is, until a speed value corresponding to the programmed action is reached and corresponding to the unwinding of a defective portion of the web from the reel 1) which is subsequently brought to the starting production value according to a predetermined acceleration ramp. In other words, the programmed actions may be appropriately anticipated with respect to the passage of the defective portions of the paper web, taking into account the inertias and delays in the execution of the actions connected to the actuators used for driving the units that make up the plant.

For example, the defect database can be associated with the specific reel by providing a barcode applied to the reel in such a way as to create a unique association between the bar code and the defects forming the database of the reel defects classified as mentioned above. The barcode can be read by a barcode reader used by an operator when loading the reel on the unwinder.

Or, the defect database can be associated with a position occupied by the reel in an automated warehouse (for example an automated warehouse with one or more conveyors-elevators possibly served by LGV trolleys) so as to form a univocal association between the position of the reel in the warehouse and the defects of forming the database of defects of the reels classified as previously mentioned, or a univocal association between that database and the trolley in use. It is understood that in any case the methods of association of the single reel defect database may vary according to the specific characteristics of the plant.

In practice, the details of execution may in any case vary in an equivalent manner as regards the individual elements described and illustrated without departing from the solution idea adopted and therefore remaining within the limits of the protection conferred by the present patent. 

1-6. (canceled)
 7. Plant for the production of paper logs, comprising: a plurality of operating units configured to produce logs of paper material starting from a web of paper material unwound from one or more corresponding reels and slaved to a control unit that, in turn, is configured for driving the operating units such that each of them has a predetermined production speed, wherein said control unit is programmed to process data contained in a database individually associated with each reel and representative of defects classified according to a predictive classification based on the effects of the defects in the production of the logs and further representative of the location of defects on the web unwound from the reel, the control unit receives position data related to the instantaneous diameter of the reel by means of corresponding detection means, the control unit is programmed to modify said production speed in function of the instantaneous position and of the class of each of said defects, and the modification of the production speed is anticipated in time with respect to the passage of a portion of the web exhibiting a defect, the predetermined production speed being modified according to a predetermined deceleration ramp until a second speed lower than the production speed is reached, followed by a predetermined acceleration ramp until the starting production speed is restored.
 8. Plant according to claim 7, wherein said operating units are an unwinder, an embossing unit and a rewinding unit.
 9. Plant according to claim 7, wherein the control unit is programmed to reduce said production speed in function of the instantaneous position and the class of each of said defects.
 10. Plant according to claim 7, wherein the control unit is programmed to make said production speed equal to zero in function of the instantaneous position and the class of each of said defects.
 11. Plant according to claim 7, wherein in said control unit resides a software program that performs said processing by using the data contained in the database and provides instructions to the control unit to change the production speed when required.
 12. Plant according to claim 7, wherein the database is recorded in a server having a data output connected with a data input of the control unit. 